The use of small particles of water in the form of fog or mist or droplets to effect evaporative cooling or to reduce the risk of frost damage to crops by creating a blanket of dispersed water particles, and to effect control of temperature and humidity for various agricultural and environmental purposes is well known. For example, U.S. Pat. No. 4,039,144 to Mee describes a system in which such results are claimed using a droplet producing nozzle having an orifice in the range of 125-400 microns which projects a stream of water against a smooth solid surface to further disperse the water stream into small sized particles. Similarly, the U.S. patent to Mee, U.S. Pat. No. 3,344,691, projects a stream of water against a pin having a curved convex surface for the same purpose.
In general, the use of nozzles which utilize streams of water under pressure to generate fogs or mists by impact against pins or other surfaces is well known as shown by the above mentioned patents as well as by others such as U.S. Pat. No. 2,701,265 to Bete el al.
Such systems produce water particles having a wide range of diameters and have not achieved the degree of effectiveness which might be possible with particles of uniform small dimensions. In the case of the Mee patents referred to above approximately half of the droplets produced have a diameter larger than 15 microns as a result of which is substantial proportion of the water is not effectively evaporated, or maintained in the form of a desired fog or mist for a sufficient period of time resulting in premature or excessive precipitation. None of these describe the generation of mists or fogs using nozzles with an orifice having a diameter of 10 microns.
The generation of a mist of water particles of the order of 10 microns through a nozzle with an orifice of that diameter, when incorporated in a system which preliminarily filters and purifies the water supply under a water pressure of 500-700 psi can effectively cool a predetermined area through flash evaporation. However, the use of a conventional type of nozzle with an orifice of such small diameter may result in problems created by deposition on or in the orifice of residual mineral materials contained in the water after prolonged use, even with careful preliminary purification and filtering.